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The Single UNIX &reg; Specification, Version 2<br>
Copyright &copy; 1997 The Open Group

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<h4>NAME</h4><blockquote>
t_sndudata - send a data unit
</blockquote><h4>SYNOPSIS</h4><blockquote>
<pre><code>

#include &lt;<a href="xti.h.html">xti.h</a>&gt;

int t_sndudata(
    int fd,
    const struct t_unitdata *unitdata)
</code>
</pre>
</blockquote><h4>DESCRIPTION</h4><blockquote>
<pre>
<P><table  bordercolor=#000000 border=1 align=center><tr valign=top><th align=center><b>Parameters</b>
<th align=center><b>Before call</b>
<th align=center><b>After call</b>
<tr valign=top><td align=left>fd
<td align=center>x
<td align=center>/
<tr valign=top><td align=left>unitdata-&gt
<td align=center>addr.maxlen
<td align=center>=
<tr valign=top><td align=left>unitdata-&gt
<td align=center>addr.len
<td align=center>x
<tr valign=top><td align=left>unitdata-&gt
<td align=center>addr.buf
<td align=center>x(x)
<tr valign=top><td align=left>unitdata-&gt
<td align=center>opt.maxlen
<td align=center>=
<tr valign=top><td align=left>unitdata-&gt
<td align=center>opt.len
<td align=center>x
<tr valign=top><td align=left>unitdata-&gt
<td align=center>opt.buf
<td align=center>?(?)
<tr valign=top><td align=left>unitdata-&gt
<td align=center>udata.maxlen
<td align=center>=
<tr valign=top><td align=left>unitdata-&gt
<td align=center>udata.len
<td align=center>x
<tr valign=top><td align=left>unitdata-&gt
<td align=center>udata.buf
<td align=center>x(x)
</table>
</pre>
<p>
This function is used in connectionless-mode
to send a data unit to another transport
user.
The argument
<I>fd</I>
identifies the local transport endpoint through which data will be
sent, and
<I>unitdata</I>
points to a
<B>t_unitdata</B>
structure containing the following members:
<pre>
<code>
struct netbuf addr;
struct netbuf opt;
struct netbuf udata;
</code>
</pre>
<p>
In
<I>unitdata</I>,
<I>addr</I>
specifies the protocol address of the destination user,
<I>opt</I>
identifies options that the user wants
associated with this request, and
<I>udata</I>
specifies the user data to be sent.
The user may choose not to specify what protocol
options are associated with the transfer by setting the
<I>len</I>
field of
<I>opt</I>
to zero.
In this case, the provider uses the option
values currently set for the communications endpoint.
<p>
If the
<I>len</I>
field of
<I>udata</I>
is zero, and sending of zero octets is not supported by the underlying
transport service, the
<i>t_sndudata()</i>
will return -1 with
<I>t_errno</I>
set to [TBADDATA].
<p>
By default,
<i>t_sndudata()</i>
operates in synchronous mode and
may wait if flow control restrictions prevent the data from
being accepted by the local transport provider at the time
the call is made.  However, if O_NONBLOCK is set (via
<i><a href="t_open.html">t_open()</a></i>
or
<i><a href="fcntl.html">fcntl()</a></i>),
<i>t_sndudata()</i>
will execute in asynchronous mode and will fail
under such conditions.
The process can arrange to be notified of the clearance of a
flow control restriction via either
<i><a href="t_look.html">t_look()</a></i>
or the EM interface.
<p>
If the amount of data specified in
<I>udata</I>
exceeds the TSDU size as returned in the
<I>tsdu</I>
field of the
<I>info</I>
argument of
<i><a href="t_open.html">t_open()</a></i>
or
<i><a href="t_getinfo.html">t_getinfo()</a></i>,
a [TBADDATA] error will be generated.
If
<i>t_sndudata()</i>
is called before the destination user
has activated its transport endpoint (see
<i><a href="t_bind.html">t_bind()</a></i>),
the data unit may be discarded.
<p>
If it is not possible for the transport provider to immediately detect
the conditions that cause the errors
[TBADDADDR] and [TBADOPT],
these errors will alternatively be returned by
<I>t_rcvuderr.</I>
Therefore, an application must be prepared to receive these errors
in both of these ways.
<p>
If the call is interrupted,
<i>t_sndudata()</i>
will return [EINTR] and the datagram will not be sent.
</blockquote><h4>VALID STATES</h4><blockquote>
T_IDLE
</blockquote><h4>ERRORS</h4><blockquote>
On failure,
<I>t_errno</I>
is set to one of the following:
<dl compact>

<dt>[TBADADDR]<dd>The specified protocol address was in an incorrect format or contained
illegal information.

<dt>[TBADDATA]<dd>Illegal amount of data. A single send was attempted specifying a TSDU greater
than that specified in the
<I>info</I>
argument, or a send of a zero byte TSDU is not supported by the provider.

<dt>[TBADF]<dd>The specified file descriptor does not refer to a transport endpoint.

<dt>[TBADOPT]<dd>The specified options were in an incorrect format or contained illegal
information.

<dt>[TFLOW]<dd>O_NONBLOCK
was set, but
the flow control mechanism prevented the transport provider from
accepting any data at this time.

<dt>[TLOOK]<dd>An asynchronous event has occurred on this transport endpoint.

<dt>[TNOTSUPPORT]<dd>This function is not supported by the underlying transport
provider.

<dt>[TOUTSTATE]<dd>The communications endpoint referenced by 
<I>fd</I>
is not in one of the states in which a call to this function is valid.

<dt>[TPROTO]<dd>This error indicates that a communication problem has been detected between
XTI and the transport provider for which there is no other suitable XTI
error
<I>(t_errno)</I>.

<dt>[TSYSERR]<dd>A system error has occurred during execution of this function.

</dl>
</blockquote><h4>RETURN VALUE</h4><blockquote>
Upon successful completion, a value of 0 is returned.  Otherwise,
a value of -1 is returned and
<I>t_errno</I>
is set to indicate an error.
</blockquote><h4>SEE ALSO</h4><blockquote>
<i><a href="fcntl.html">fcntl()</a></i>,
<i><a href="t_alloc.html">t_alloc()</a></i>,
<i><a href="t_open.html">t_open()</a></i>,
<i><a href="t_rcvudata.html">t_rcvudata()</a></i>,
<i><a href="t_rcvuderr.html">t_rcvuderr()</a></i>.
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Copyright &copy; 1997 The Open Group
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